Hydrophobic Matrices Research Articles

Synthesis of bio-polyol-functionalized nanocrystalline celluloses as reactive/reinforcing components in bio-based polyurethane foams by homogeneous environment modification

Nanocrystalline Cellulose (NCC or CNC) is widely used as a filler in polymer composites due to its high specific strength, tensile modulus, aspect ratio, and sustainability.However, CNC hydrophilicity complicates its dispersion in hydrophobic polymeric matrices giving rise to aggregate structures and thus compromising its reinforcing action. CNC functionalization in a homogeneous environment, through silanization with trichloro(butyl)silane as a coupling agent and subsequent grafting with bio-based polyols, is herein investigated aiming to enhance CNC dispersibility improving the filler-matrix interaction between the hydrophobic PU and hydrophilic CNC. The modified CNCs (m_Ci) have been studied by XRD, SEM, and TGA analyses. The TGA results show that the amount of grafted polyol is strongly influenced by both its molar mass and OH number and the maximum amount of grafted polyol reaches up to 0.32 mmol per grams of functionalized CNC, within the explored conditions. The effect of different concentrations (1–3 wt%) of m_Ci on the physical, morphological, and mechanical properties of the resulting bio-based composite polyurethane foams is evaluated. Composite PU foams present compressive modulus up to 4.81 MPa and strength up to 255 kPa more than five times higher than those reinforced with unmodified CNC or with modified CNC in heterogeneous chemical environment. The improvement of mechanical properties of the examined PU foams, as a consequence of the incorporation of bio-polyols modified CNCs where polyol's OH groups interact with polyurethane precursors, could further broaden the use of these materials in building applications.

Investigating the Reactive Reinforcement Ability of Maleic Anhydride-Modified Cellulose Nanocrystals via In-Situ Emulsion Polymerization.

CNC-based nanocomposites have gained substantial interest because of their enhanced thermomechanical properties for high-end engineering applications. The chemical modification of CNCs expands their applicability, making them suitable for use in hydrophobic polymer matrices. The current study investigates the reactive reinforcing ability of maleic anhydride-modified cellulose nanocrystals during the in situ polymerization of a vinyl monomer, i.e., styrene. Highly crystalline nanocellulose (CNCBG) was isolated from Lagenaria siceraria (Bottle gourd) peels via Hydrochloric acid, which was further modified to synthesize maleic anhydride-modified cellulose nanocrystals (MACNCBG) and characterized employing various techniques. MACNCBG exhibited higher suspension stability than CNCBG due to the introduction of carboxyl groups. Furthermore, polystyrene-based nanocomposites of 3 and 5 wt % filler loading were prepared, respectively. While PSMACNCBG (5 wt %) displayed a premature failure, PSMACNCBG (3 wt %) demonstrated enhanced mechanical properties compared to PSCNCBG (3 wt %) and PS. At the same filler loading, MACNCBG demonstrated a more remarkable reinforcing ability than CNCBG, owing to its reactive tendency. The appearance of a new peak between 3000-2800 cm-1 corresponds to the C-H stretching of the formed C-C bond (between C=C of MACNCBG and benzal carbon of PS) in the FTIR spectra, confirming the reactive nature of MACNCBG.

Preparation and Characterization of Cellulose Nanocrystal‐Doped Cellulose Triacetate Optical Films by Sol‐Gel Process

AbstractA bio‐based nanocomposite optical film was obtained through a simple sol‐gel process and solution casting. The dispersion effect of cellulose nanocrystals (CNCs) gel and the optical properties, mechanical performance and thermal stability of CNC‐doped cellulose triacetate (TAC) films (TAC−X) were systematically evaluated. The results show that CNCs can be well dispersed in hydrophobic organic solvents and TAC matrices through the sol‐gel process. TAC−X film has excellent optical properties, its light transmittance is above 92 %, its haze value and birefringence are low, ranging from 0.21±0.01 % to 0.38±0.02 %, and (1.64±0.26)×10−6 to (2.49±0.50)×10−6 respectively. When doped with 2 wt % CNCs, the tensile strength and Young's modulus of the TAC‐2 film were 33.0 % and 30.1 % higher than those of the pure TAC film, separately. At the same time, the TAC−X film also maintains good thermal stability, with its glass transition temperature and maximum decomposition temperature falling between 215–216 °C and 366–368 °C respectively. The simple sol‐gel process provides a convenient and efficient way to use CNCs doping to enhance the physical and mechanical properties of TAC optical films.

A Review on Surface Modification of Plant Fibers for Enhancing Properties of Biocomposites

AbstractOver the past decade, significant progress has been made in creating environmentally friendly products using natural resources. Plant fibers, also known as lignocellulosic fibers, are hydrophilic due to the interaction and attraction between water molecules and the hydroxyl groups present in their components. The inherent hydrophilicity of plant fibers often prevents them from interacting effectively with hydrophobic polymer matrices. In order to improve the adhesion between plant fibers and the matrix, it is necessary to modify the surface of the fibers. Commonly used chemical processes include mercerization, silane treatment, acetylation, permanganate treatment, acrylation, benzoylation, peroxide treatment, stearic acid treatment, isocyanate treatment and sodium chlorite intervention. The desirability of chemically modifying the surface of plant fibers has declined due to several limitations. Plant fibers can be modified in an environmentally friendly way by various methods, such as plasma therapy and treatments using fungi, enzymes and bacteria. This part provides an analysis of the impact of different environmentally friendly surface modification techniques on the properties of plant fibers and reinforced polymers.

Critical assessment of the thermal stability and degradation of chemically functionalized nanocellulose-based polymer nanocomposites

Abstract In the last century, global awareness of the environmental repercussions associated with petroleum-based polymer composites has surged. This realization urged extensive scientific research directed towards plant-based biomass, particularly nanocellulose, as a reinforcing element in polymer matrices. Global market value of nanocellulose is expected to increase considerably by 2025, to a forecast USD 783 million. Despite nanocellulose’s performance benefits, its poor compatibility with hydrophobic polymer matrices poses challenges, limiting thermal stability and impeding widespread commercialization at higher processing temperatures. To overcome these issues, chemical modification or functionalization emerges as a promising solution to enhance nanocellulose-based polymer nanocomposites’ thermal stability. The abundance of hydroxyl groups on nanocellulose enables specific chemical modifications, such as grafting functional molecules or forming covalent/ionic bonds with the polymer matrix. The aim of this study is to validate that integrating chemically functionalized nanocellulose into various polymer matrices, including thermoset, thermoplastic, and bio-polymer, enhances the thermal stability of resulting polymer nanocomposites, supported by thermogravimetric analysis (TGA). The study also explores six additional factors influencing TGA in nanocomposites, providing a comprehensive understanding of elements impacting the thermal properties of these materials.

Surface Modification of Montmorillonite Clay Towards the Fabrication of Nanocomposites for Engineering Applications

Montmorillonite (MMT) is a layered clay mineral composed of silica and alumina sheets with a layer thickness of about 1 nm qualifies it as a two-dimensional nanomaterial. MMT is found in natural clay ores in the Murunkan, Kirinda, and Okanda areas in Sri Lanka. Nanocomposites with enhanced physical and mechanical properties can be prepared by dispersing MMT in a polymer matrix. However, the hydrophilic nature of MMT hinders the incorporation of MMT into hydrophobic polymer matrices. Hence, a suitable surface modification is required to make MMT compatible with polymers. The present study was based on the preparation and analysis of organically modified calcium Montmorillonite (Ca-MMT)-polypropylene nanocomposites as a green technology initiative. Homo-ionic Ca-MMT was prepared by treating commercial MMT-K10 with a CaCl2 solution. The predominant exchangeable divalent cations present in MMT-K10 and Ca-MMT were determined using AAS. The cation exchange capacity of Ca-MMT was about two times greater than that of MMT-K10. Furthermore, XRD analysis showed a slight increase in d- spacing of Ca-MMT compared to MMT-K10. A novel ligand, triethylene glycol dodecyl methyl ether was synthesized by treating triethylene glycol monomethyl ether (TGME) with 50% w/w aqueous solution of sodium hydroxide followed by 1-bromododecane with the molar ratio of TGME:NaOH:1-bromododecane in 1:2:2. The crude product was purified by column chromatography and characterized by FTIR and GCMS analysis. Hydrophilic Ca-MMT was surface modified with the organic ligand presumably via the coordination of triethylene glycol moiety with Ca2+ cations at the outer edge of the MMT particles. The long aliphatic chains in the periphery of the modified MMT particle make it more organophilic. Modified Ca-MMT was characterized by XRD, TGA, and FTIR analysis. The XRD revealed a slight increase in the d-spacing related to the 001 plane of modified Ca-MMT compared to unmodified clay. The effect of modified Ca-MMT loadings (0.5%, 1%, and 1.5%) on the mechanical properties of the nanocomposite was studied. The results implied an enhancement of the mechanical properties in terms of impact resistance, hardness, and flexural properties in the nanocomposite compared to the virgin polymer. The fabricated nanocomposite is a promising engineering material that may have applications in automotive, construction, and packaging products.
 
 Keywords: Montmorillonite, Polypropylene, Nanocomposite, TGME, Compatibility

Assessing Eco-Friendly Alternatives: Composite Fibers and Recycled Plastics for Sustainable Impact and Efficiency

The chase for sustainability has driven awesome strides in composite fibers and recycled plastics, which have made viable options available in numerous areas. Composite fibers are known for their recordbreaking strength-to-weight proportions and capacity to serve numerous functions, that’s why they’re used all over from the automotive industry to aviation. But natural fibers are hydrophilic, so they do not mix well with hydrophobic matrices they need surface adjustments and fire retardant treatments to be utilized for composites to perform at their best. On the other hand, one of plastics’ most significant benefits is their recyclability, recycling programs can do a lot to tackle widespread plastic contamination. Recycling has positive environmental effects, but still there are major challenges when it comes to plastic recycling including contamination and all the different types of plastics that require sorting out. Promising answers can be offered to these issues through better approaches to sorting and recycling plastic waste. For instance, life cycle assessments and carbon footprint research are vital for deciding how much composite fibers influence the environment in comparison with conventional materials made from recycled plastics. In this study, we can see that all through their lifecycle composite fibers have been found to discharge minimal amounts of GHGs subsequently reducing energy use to reduce pollution. Similarly, the work on recycled plastics when compared with virgin ones lowers their impacts on the environment by saving landfills from plastic waste, reducing the demand for raw materials, and high in energy production techniques. In general terms, sustainable indicators are exceptionally imperative in ensuring that we make choices based on reliable information regarding environmentally sustainable practices and industrial applications that require solid and sustainable future transformation.

Toward a zero-waste microalgal biorefinery: Complete utilization of defatted Chlorella biomass as a sole heterotrophic substrate for Chlorella sp. HS2 and an improved composite filler

The concept of circular biorefinery has been promoted as a sustainable new approach for the nascent microalgae industry. In particular, solvent extraction of the lipid fraction of microalgal biomass is generally performed when aiming to recover marketable compounds from microalgae; the waste residual biomass generated by this process can provide new market opportunities for microalgae in a wide array of commercial sectors. Herein, the heterotrophic cultivation of Chlorella sp. HS2 was demonstrated using a hydrolysate recovered following the dilute acid hydrolysis of defatted Chlorella biomass (DCB). While HCl and H2SO4 in each case was found to be an effective catalyst capable of converting nearly 40% of DCB into fermentable monosugars, the results of microalgal cultivation in diluted hydrolysate indicated high cellular growth without the need for any supplemental nutrients. Notably, the highest microalgal growth was observed when neutralizing HCl- and H2SO4-treated hydrolysates with NaOH and Ca(OH)2, respectively. Furthermore, the fabrication of a polymer/residual composite using the residual material obtained after H2SO4-catalyzed hydrolysis and Ca(OH)2 neutralization suggested improved tensile capabilities, attributed to the improved dispersion of salt precipitates-containing residue in the hydrophobic polymer matrices. Considering that the leftover residual DCB could be better conditioned as an organic–inorganic filler for composite fabrication through a combined acid hydrolysis-neutralization process, the results here suggest new integrated utilization routes for underutilized byproducts from the microalgal industry. Further investigations are thus warranted with a special focus on bolstering the economic feasibility and scalability of the postulated zero-waste microalgal biorefinery.

Applicability of a central force water model to study adsorption in disordered hydrophobic matrices—replica Ornstein–Zernike theory

A simple central force water model to study adsorption in random Lennard-Jones-like matrices has been studied using the replica Ornstein–Zernike integral equation theory in hypernetted-chain (HNC) approximation and in HNC+bridge approximation. The structure of water in obstacle matrices of different sizes was studied, showing that the model appropriately accounts for the hydrophobic hydration. By calculating the chemical potential of water in the model adsorbent, we have constructed the adsorption isotherm. Except for the cases of highly dispersed matrices, water gets excluded from the crowded hydrophobic environment, as expected experimentally.

A review of nanocellulose modification and compatibility barrier for various applications

Nanocellulose is increasingly important due to its abundance and sustainability sources, outstanding physicochemical properties, low density, high specific surface area, and easily modified surface chemistry. Nanocellulose is obtained from various sources, such as plants, algae, and bacteria, with plant-derived nanocellulose being the most common. Their presence significantly benefits many applications, especially in developing advanced materials for high end-use. Despite these benefits, the intrinsic hydrophilic behavior complicates dispersion in hydrophobic polymer matrices due to aggregation issues that result in deterioration properties. Nanocellulose modification and surface tuning are identified as fundamental approaches for improving the compatibility of the interfacial interaction between nanocellulose and polymer matrix to impart new functionalities to novel advanced materials. This article offers insight into nanocellulose by highlighting various lignocellulosic biomass sources and their chemical constituents. Three categories of nanocellulose are discussed in this review, including cellulose nanocrystals, cellulose nanofibrils, and bacterial nanocellulose. This article also featured several methods for promoting surface modification of nanocellulose to overcome the compatibility barrier between nanocellulose and polymer matrix to achieve a balanced hydrophilic-hydrophobic behavior. A few recent and emerging applications of nanocellulose-based composites are also presented in this review.

Thermal stability of natural fiber reinforced biodegradable composites

Polymer composites reinforced with natural fibers are being increasingly developed by researcher and scientist in the recent field of material science due to their various applications in aerospace, marine and industries. The hydrophilic natural fibers are incompatible with the hydrophobic polymer matrices this leads to less interfacial bonding between fibers and matrix. In this paper, fibers were collected from desert plant prosopis juliflora and NaOH treatment was done to increase interfacial bonding of fiber-Matrix. Prosopis Juliflora fiber reinforced phenol formaldehyde composites were prepared with different fiber loading up to 20wt% and then characterized by thermo gravimetric analysis. This paper describes thermal properties composites materials by Thermo gravimetric analysis TGA and Differential scanning calorimetric DSC analysis of composite materials with different heating rates and hence establishes a connection between temperature and physical properties of substances. This study highlights the potential of alkali treatment in improving the thermal stability of the composites. This paper concludes that by, increasing the fiber weight percentage (fiber loading) in PF resin does increase the thermal stability of the resulting composite. The mass residue of untreated fiber reinforced PF composites with fiber loading 15% wt. UTFRPFC 15was 35%, while treated fiber reinforced PF composites with fiber loading 15% wt. ATFRPFC 15 had a mass residue of 75% at a temperature of 400°C. This clearly shows that alkali treatment significantly enhances the thermal stability of the composites. Alkali pre-treatment activates the fibers’ surface and helps increase the fiber’s mechanical strength.

A new RPLC-ESI-MS method for the determination of eight vitamers of vitamin E

Vitamin E consists of four (α-, β-, γ-, δ-) isoforms of tocopherols (T) and tocotrienols (T3), collectively known as tocols. Current LC methods for tocols suffer from either the poor ability to resolve the β- and γ- isoforms (RPLC), or require the use of nonpolar solvents (NPLC), which complicates subsequent MS/MS detection. Moreover, we show that coupling of UV with MS leads to tocols photodegradation. To solve these problems, we developed a new RPLC-MS/MS method, allowing to resolve not only α- and δ-, but also β- and γ- tocols in hydrophobic matrices. We took advantage of an observation that the peak area ratios are specific for the given isomer and constant. The new method with a linear range between 0.2 and 60 ng·mL−1 (for α-T) and 1.1–60 ng·mL−1 (for β-T3 and γ-T3) was validated and employed for quantitative analysis of several oils, including false flax (Camelina sativa) oil stored under different conditions.

Cellulose nanocrystal and Pluronic L121-based thermo-responsive composite hydrogels

Cellulose nanocrystal (CNC) is a promising sustainable material with its biocompatibility, high aspect ratio, and mechanical strength. CNC-based systems have potential applications in various fields including biosensors, packaging, coating, energy storage, and pharmaceuticals. However, turning CNC into smart systems remains a challenge due to the lack of stimuli-responsiveness, limitation in compatibility with hydrophobic matrices, and their agglomeration tendency. In this work, a thermo-responsive nanocomposite system is constructed with CNCs and polymersome forming Pluronic L121 (L121), and its phase behavior and mechanical properties are investigated in detail. Two different CNC concentration (4 % and 5 %) is studied by changing the L121 concentration (1–20 %) to understand the effect of unimers and polymersomes on the CNC network. At dilute L121 concentrations (1–5 %), the composite system becomes softer but more fragile below the transition temperature. However, it becomes much stronger at higher L121 concentrations (10–20 %), and a gel network is obtained above the transition temperature. Interestingly, the elastically reinforced CNC gels exhibit greater resistance to microstructural breakdown at large strains due to the soft and deformable nature of the large polymersomes. It is also found that the gelation temperature for hydrogels is tunable with increasing L121 concentration, and the nanocomposite hydrogels displayed thermo-reversible rheological behavior.

Centrifugally spun hybrid polyhydroxyalkanoate/dextran nanocapsule fiber matrix for the delivery of hydrophilic payloads

Biopolymeric micro- and nanofibers with active ingredients have gained significant attention for biological applications. However, the incorporation of hydrophilic compounds into hydrophobic matrices via spinning techniques remain rather unexplored. Here we report the incorporation of dextran nanocapsules (Dex-NCs) in centrifugally spun poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) fibers for the release of hydrophilic payloads. Inverse miniemulsion polymerization was employed to synthesize hydrophilic Dex-NCs with an average size of 0.25 µm. The Dex-NCs were embedded into PHBHHx via dual solvent centrifugal spinning at 0–7 wt% loading, resulting in beaded fibers with average fiber diameters of 4–6 µm. The effect of Dex-NC loading on the melting and crystallization behavior of PHBHHx was limited, while the strength and stiffness of the hybrid fibers was retained. The elongation of the hybrid fiber mats is reduced with increasing Dex-NC loading, but remains suitable for biological applications. Further, the in vitro release measurements showed a time dependent release of embedded Dex-NCs and the payload from the hybrid fibers. We anticipate this hybrid fiber matrix to be a starting point for the development of non-woven mats for slow release of hydrophilic payloads for biological applications, especially for medical wound dressings.

Modulation of surface properties of cellulose nanocrystals through adsorption of tannic acid and alkyl cellulose derivatives

Cellulose nanocrystals (CNCs) are hydrophilic nanoparticles that cannot be dispersed in non-polar solvents or hydrophobic polymer matrices. Here, we demonstrate the tunable modification of CNC surfaces by physical adsorption of tannic acid (TA) and two alkyl cellulose derivatives (ACDs), methyl cellulose (MC) and ethyl cellulose (EC), while maintaining their sustainable nature. We compare the impact of ACD adsorption when mixed with CNCs to CNCs precoated with tannic acid (CNC@TA), varying ACD weight fractions in CNC suspensions. Our results show that CNC@ACD and CNC@TA@ACD aqueous suspensions display good colloidal stability in water, while their surface properties are altered. We use a wide range of analytical techniques to characterize these suspensions, with a focus on their interaction with water. The two selected ACDs adsorb on both CNCs and CNC@TA at low fractions (ACD ≤ 10 % w/w), followed by an intermediate region of saturation between 10 % and 30 % w/w. At fractions above 30 % w/w, we observe the formation of CNC- or CNC@TA-reinforced ACD composites. Most samples can be redispersed in water upon freeze-drying, except for EC-rich samples redispersible in toluene. Our facile method for preparing ACD-coated CNCs allows for the creation of a range of nanomaterials with modulable wetting and emulsification properties.

Cellulose nanocrystal/polymer nanocomposite latex via surfactant-free emulsion polymerization

Polar cellulose nanocrystals (CNCs) are difficult to disperse well in hydrophobic polymer matrices, and usually surfactants or expensive and time-consuming functionalization of the reinforcement or matrix have been attempted to improve dispersion. Here, we report a new, facile method to prepare CNC/polymer nanocomposite latices directly via surfactant-free emulsion polymerization of vinyl monomers and CNCs initiated by a cationic, water-soluble, free-radical initiator. The distribution of CNCs in the latex particles can be tailored through controlling the reaction procedures, namely, whether the monomers are added before or after preheating the CNCs with the initiator and has been confirmed by scanning electron microscopy (SEM) and scanning transmission X-ray microscopy (STXM) studies. CNCs distribute inside the latex particles if the monomers are added after the preheating step, and owing to the more even distribution of CNCs, such nanocomposite latices exhibit better mechanical properties than those prepared without preheating or via physically mixing CNCs with emulsions polymerized using conventional surfactant system. A latex particle formation mechanism is proposed based on these phenomena and polymerization kinetics studied in this work. Unlike typical CNC-based Pickering emulsion polymerization, our process can be operated without the need for intense mechanical shearing and provide an industrially scalable approach to prepare stable CNC/polymer nanocomposite latices that can be melt processed or used directly in a variety of applications, such as paints and coatings, adhesives, or cosmetics.

Novel Use of Cellulose Based Biodegradable Nano Crystals in the Machining of PPS Composites: An Approach Towards Green Machining

Because of their biodegradable and regenerative properties, cellulose nanocrystals derived primarily from naturally occurring cellulose fibers serve as a sustainable and environmentally beneficial material for most applications. Although these nanocrystals are inherently hydrophilic, they can be surface functionalized to suit a wide range of demanding requirements, such as those associated with the creation of high-performance nanocomposites in hydrophobic polymer matrices. Therefore, the present work deals with the application of cellulose-based biodegradable nanocrystals as a lubricant in the machining of PPS composites. In this study, milling process was considered to investigate the influence of the sustainable lubricating conditions on the machinability indexes of PPS composites. As a novel cooling approach, water-based solutions enriched by cellulose nanocrystals with different reinforcements (0.25%, 0.5%, and 1%) were used over known methods such as MQL, conventional flood, and dry. According to the research outcomes, cellulose nanocrystals-based nanofluids provided satisfying contributions on retarding the tool wear and reducing the cutting temperatures considerably. Despite the surface-related results such as roughness, topography and texture are promising for the developed strategy; further investigations will be useful to determine ideal water-particle concentration to improve the quality of the machined surface.

Synthesis of Hydrophobic Block Copolymer Nanoparticles in Alcohol/Water Stabilized by Poly(methyl methacrylate) via RAFT Dispersion Polymerization-Induced Self-Assembly

Poly(methyl methacrylate) (PMMA) is an important common polymer widely used in industry. While PMMA has been used as a core-forming block for polymerization-induced self-assembly (PISA), a powerful approach for the synthesis of block copolymer nanoparticles, it has not been utilized as a corona block due to PMMA being insoluble in common solvents for PISA formulations (e.g., water and alcohols). Exploiting the solubility of PMMA-dithiobenzoate (DTB) in ethanol/water mixtures, such macroRAFT agents have in the present work been successfully employed for reversible addition–fragmentation chain transfer (RAFT) PISA in ethanol/water (80/20 by volume). RAFT dispersion polymerization of benzyl methacrylate mediated by PMMA-DTB macroRAFT agents with various degrees of polymerization has been investigated. Transmission electron microscopy analyses revealed well-defined block copolymer nano-objects, including spheres, worms, as well as vesicles. Nanoparticles comprising a PMMA outer layer would have superior compatibility with various hydrophobic polymer matrices, thereby enabling various new applications such as, e.g., use as nanofillers.

Effects of alkaline treatment on the properties of pineapple (Ananas Comosus) leaf fiber (Palf) reinforced with tapioca-based bio resin (Cassava Starch)

The poor compatibility of natural fibers with hydrophobic matrices due to their hydrophilic nature has led researchers to improve their properties to enable better compatibility. Pineapple leaf fiber is one of the abundantly available natural fibers obtained from pineapple leaf. It has good chemical properties and strong admirable mechanical properties and can be used as a replacement for synthetic fibers despite the same deficiencies as other natural fibers. In this study, Pineapple leaf fiber was treated with Alkali at varying concentrations, temperatures, and times. Treated pineapple leaf fiber was reinforced with tapioca-based bio resin (cassava starch). This fiber was subjected to tensile testing and Fourier transform infrared (FTIR) spectroscopy. The results of FTIR indicated the various peaks in the absorbance versus wave number relation. The FTIR analysis of untreated pineapple leaf fiber indicated the presence of O-H stretch, N-H stretch, C ≡ stretch, C=O stretch, and H-C-H bond. The modification of fibers achieved by disruption of hydrogen bonding in the network structure was possible due to its treatment with alkali. Mechanical testing (tensile test) and FTIR were also used to know the effects of chemical treatment on the fibers. Alkali treatment improved the fiber properties as the concentration, temperature, and treatment time increased.

Progress of Hydrophobic Ionogels: A Review.

The emergence of hydrophobic ionogels composed of hydrophobic polymer matrices and hydrophobic ionic liquids has drastically broadened the applications of ionic devices, especially for underwater explorations. Compared with traditional ionogels, hydrophobic ones are capable of achieving long-term stability in ambient and aqueous environments. In this review, the latest research developments of intrinsically hydrophobic ionogels are summarized, with particular emphases placed on the materials, mechanisms and applications. The basic issues about hydrophobic ionogels, including the material systems, dynamic gelation bonds and network structures are elucidated. The up-to-date advent of the ambient/underwater applications of hydrophobic ionogels concerning adhesion, self-healing, and sensing are comprehensively summarized. Special attention is paid to underwater scenarios considering the rapid development of marine explorations and the intrinsic properties of hydrophobic ionogels. Finally, the current challenges and immediate opportunities of this emerging yet fast-developing research field are discussed.